I know you are aware, and you also know that "the consent of the dead" is impossible, which makes it all the more painful :-)
Your Sondheim followup helps make my point a little. Your point (with which I disagree but that I am pretty sure I understand) is that radical revision should die with the artist. And yet you seem to acknowledge (or at least recognize the possibility that) an author might want his work to be revised in the future (to remain resonant or whatever). So other than your own intuition, what is the basis for suggesting that the estate is doing something the dead dudes wouldn't like?